The present invention relates generally to a drive apparatus for elevators and, in particular, to a gearless drive machine for elevators.
There is shown in the U.S. Pat. No. 4,679,661 a drive machine of modular construction having a housing with endcaps of cylindrical shape at one end and frusto-conical shape at the other end. The frusto-conical front endcap has a tubular boss extending outwardly from its center and a shaft projects from both sides of the boss and is supported by a double roller bearing mounted in the boss. A drive pulley is attached to the outwardly projecting shaft portion at the front endcap. The end of the shaft projecting into the housing carries a not-illustrated rotor which is encompassed by a not-illustrated stator arranged in the housing to form an electric motor. The rear cylindrical endcap has a third not-illustrated bearing for supporting the inwardly projecting end of the shaft. The housing has a flange which is detachably connected with the front endcap for replacing the motor.
A disadvantage of the above-described equipment is that high bending moments are caused by the mechanical structure and must be taken into consideration in the design of the machine frame. A further disadvantage is that, due to the three bearing support of the shaft and due to the double bearing outside arrangement of the drive pulley, the bearings and the shaft are exposed to an excessively high mechanical stressing. Apart from the mechanical inadequacies, a further disadvantage is that an on-site assembly of the drive machine is not possible due to the complex mechanical construction.